Without schemas

I made a mistake and sent my post personally to Chander Ganesan, here it is:

Have you used PHP with PostgreSQL?? (Especifically the Doctrine
Framework??). Because my question arises from the fact that I've had
problems when rying to use Doctrine with a PostgreSQL database and I thought
that the reason could be the lack of the schema name. However, according to
your answer, it is not necessary to put the schema name before the table's
(when it comes to the public schema). I'm trying some code right now and
I've figured out that it's not the same to use 'SELECT NICK FROM USUARIOS'
vs. 'SELECT "Nick" from "Usuarios"', it only works the second way. So, my
problem could have something to do with it??